TV tonight: 'Vampire Diaries,' 'Mom'

The Vampire Diaries
CW, 8 ET/PT
As Diaries reopens, Kai (guest star Chris Wood) is still holding Elena captive, and still trying to get total control over his newly acquired powers. But that's just the headline: As always here, many other plots and characters are spinning at the same time, like plates on sticks. And keeping them spinning tonight behind the camera is star Paul Wesley, who directed the episode.
Mom
CBS, 8:30 ET/PT
If you're a fan of this fascinating sitcom, you won't want to miss tonight's outing, which sends the show in an unexpected new direction and mixes tones in ways few other comedies attempt. The shifts can sometimes feel abrupt, but once you're in the moment with the characters, the actors (particularly Allison Janney and Mimi Kennedy) bring enough truth to the scene to keep you fixed there, at least until you're jolted into another mood. Oh, and if you are a fan, try not to read or hear any plot details about the episode, because any description is likely to clue you in to where the story is headed and ruin the surprise.
Bad Judge/A to Z
NBC, 9 ET/PT
Two ill-conceived sitcoms wind down, but don't get your hopes up. The next combo NBC has in store for this slot, Undateable and One Big Happy, is no better — and may be even worse.